U.S. Pat. No. 1,883,296 to Johnson discloses a prism mounted to the side of a windshield, which prism is used as an observing instrument for observing traffic ahead of the vehicle.
U.S. Pat. No. 2,514,989 to Buren discloses a plain mirror employed next to the side view mirror, which can be tilted outward to view the blind spot area. It could cause discomfort to the driver's eye such as tilting the mirror in an opposite direction of view. It requires the driver to focus for longer time than necessary to establish the image of the other vehicle.
U.S. Pat. No. 3,151,207 to Moller discloses two plain mirrors employed on top of the rear view mirror inside the vehicle. This type of device does not give adequate blind spot viewing.
U.S. Pat. No. 4,182,552 to Feinbloom discloses in FIG. 3 a plain mirror with a wedge on the back to tilt the mirror outward to view the blind spot area. In FIG. 4 of the Feinbloom patent, which figure is reproduced as FIG. 8 of this application, discloses a prism 4 mounted on a side view mirror in a base out position. The prism serves to deflect the light from the rear of the automobile directly upon the mirror surface of the mirror 3. In this manner the original mirror 3 is employed and the prism alters the light to provide the field of view of the blind spot by bending the light rays.
U.S. Pat. No. 5,245,479 discloses a rear view mirror which also utilizes a prism, this device being similar to the Feinbloom rear view mirror in that a clear prism is mounted on a mirrored surface.
Other forms of rear view mirrors utilizing prisms are well known in the art. For example U.S. Pat. No. 3,708,222 discloses a Fresnel mirror which comprises a plurality of concentric annular prisms. Another rear view mirror is shown in U.S. Pat. No. 3,619,038 which utilizes a prism for a day/night mirror.
In addition to the prior art set forth above, convex mirrors of varying shapes are also employed. One such example is shown in U.S. Pat. No. 4,311,363 to Marsalka et al.
It would suffice to say that while various configurations of mirrors and prism assemblies are depicted in the prior art, these prior art devices distort the field of view or are extremely complicated and require frequent adjustment and maintenance. In addition, non of these devices utilize the internal reflection of a prism.